Electrical connectors having secondary lock members are well known in the art. These connectors provide a secondary locking member for cooperating with a latch to assure that contacts are properly secured. The secondary lock member typically is wedged between the latch and some backup surface inside the housing to ensure that the latch remains seated in the contact when a pulling force is applied.
An example of such a connector is shown in U.S. Pat. No. 4,740,437 by Dyki. This patent shows a separable electrical connector for a plurality of axially connectable cylindrical electrical terminals adapted for coupling to the threads of insulated wires and having an annular external recess on each of the terminals. The connector includes a tubular housing having a plurality of apertures extending axially therethrough and a plurality of outboard ramping retention abutments formed integrally with the housing upon at least one inner surface of a radially outboard portion of the housing. A plurality of axially extending terminal guide fingers is included upon a central land located within the housing. A spacer engages the central land for displacing the terminal guide fingers in the direction of the ramping retention abutments so that the terminals will be retained securely within the connector housing.
Another example of such a secondary locking device is shown in U.S. Pat. No. 3,601,410 by Cairns. This patent teaches an electrical connector including both a terminal having an annular recess and a housing having an aperture therein for receiving the terminal. A flexible wall forms a portion of the housing and this wall extends along and defines at least a portion of the length of the housing's terminal receiving aperture. A locating tab secured to the flexible wall enters the annular recess of the terminal to position it within the receiving aperture. A locking device is attached to the housing to prevent the free flexing of the flexible wall when the tab has positioned the terminal within the aperture.
In both of these patents, it should be noted that the terminals are completely surrounded by insulative housing material to avoid the risk of electrical shock to a user when the connectors are in an unmated condition. In a connector with a relatively small number of terminals, for example, two rows of two or three terminals, forming the housing to have insulative walls that extend around each contact and between each contact is a relatively common practice. However, in applications where it is desirable to achieve higher terminal densities, for example more than two rows of terminals within a relatively small housing, a problem exists in that forming the housing to insulate each terminal will unduly increase the size of the housing.
An additional problem exists with the connectors shown in these patents when it is desirable to achieve higher terminal densities by adding rows. For example, in both of these patents, it can be seen that a secondary locking member is positioned between two rows of adjacent terminals. In the event that it is desirable to achieve more than two rows of terminals, additional secondary locking devices would be required for the additional rows thus creating the need for additional space adjacent to each row to receive the secondary locking devices. This will also increase the overall size of the connector housing.
In addition to these problems, in applications where many plugs and receptacles are present it is desirable to prevent mating of a plug with the wrong receptacle.